This is the return vent . Cold air is blown in at the top drops and is sucked into the vent at the bottom. The vent leads to the freezer at the bottom of the evapator . If it is blocked by ice. Air can not return to the freezer side so you will not get any cooling in the fresh food side.

This is the return vent . Cold air is blown in at the top drops and is sucked into the vent at the bottom. The vent leads to the freezer at the bottom of the evapator . If it is blocked by ice. Air can not return to the freezer side so you will not get any cooling in the fresh food side.

This makes sense. I've got the thing back together now so I can't see the down by the evaporator. I'm guessing there has to be some sort of blockage on the freezer side not letting the cold air back into the freezer side.